The purpose of this research is to investigate how the knowledge of second language is learned or acquired and how lexical reference tools such as dictionaries can help learners facilitate the learning process. We focused on the lexical knowledge of L2 learners, especially the ability to recognize and produce in English. To achieve this goal, we have developed the system of dictionary and lexicon servers, which have the following main functions :a) Dictionary servers: one can look up and compare words across different dictionaries (more than 50 titles) at one clickb) Mega-corpus server: British National Corpus on the Web (the system developed by University of Zurich)c) Japanese Newspaper corpora: original text archives of major Japanese newspapers (Mainichi, Yomiuri, Asahi for more than 10 years)d) English-Japanese parallel corpora: parallel texts (Yomiuri Shinbun vs. Daily Yomiuri)Using these lexical databases and corpora, we worked in the following three groups:1) Theoretical Linguistics Group: Haraguchi, Tsurusaki2) Pragmatics/Sociolinguistics Group: Tanaka, Kawanari3) Lexicography Group: Yamagishi, TonoEach group aimed to propose some findings about the characteristics of English lexical knowledge from their professional research perspectives, and to suggest pedagogical applications for the contents of learner's dictionaries.In the final report, various aspects of English words and their rules in actual contexts of language use were identified and some pedagogical implications were drawn with the view to improving the information in pedagogical dictionary making.